devel/android-tools-adb-devel: add new slave port for git master

A temporary port to facilitate testing and updating master.

While copying usb_libusb.c [1] under FILESDIR clean it up:

• Add static keyword for file-local functions
• Fix const usage exposed in C++ mode [2]
• Fix casting 3rd argument of libusb_bulk_transfer(3) exposed in C++ mode
• Fix inconsistent whitespace: trailing, tabs + spaces, bogus indentation
• Fix typo in usb_kick() trace message
• Fix fprintf(3) warning in scan_usb_devices() trace message
• Convert err(3) usage to fatal_errno()
• Drop BSDism of sysexits(3)
• Drop unecessary struct keyword
• Drop unused headers [2]
• Explicitly include <signal.h> header

And chase the following commits:
https://android.googlesource.com/platform/system/core/+/506aea4%5E!/ [1]
https://android.googlesource.com/platform/system/core/+/dc3b459%5E!/#F3
https://android.googlesource.com/platform/system/core/+/9b0f354%5E!/#F5
https://android.googlesource.com/platform/system/core/+/cf07494%5E!/#F8
https://android.googlesource.com/platform/system/core/+/3313426%5E!/#F20
https://android.googlesource.com/platform/system/core/+/7664901%5E!/#F18

Changes: https://android.googlesource.com/platform/system/core/+log/53d504f/adb
Differential Revision: https://reviews.freebsd.org/D2870
Obtained from: devel/android-tools-fastboot-devel (based on)
Obtained from: OpenBSD ports [2]
Approved by: kevlo (maintainer)